Such safety valves may be provided with an inlet port, two working ports and two outlet ports and used for cooperating with pressure actuated working elements as e.g. double acting cylinder of presses. The safety valves include two parallel valve spindles actuated by suitable pilot valves which communicate with pertaining reservoirs to supply the required pressure. Each of the valve spindles is provided with a working piston and a valve piston with the valve pistons linked to each other via crossing channels.
Safety valves of this kind are used in the technical field e.g. for controlling the clutch and brake of eccentric presses. In devices, however, which are actuated bidirectional e.g. double acting cylinders, control systems are used which for safety reasons are very complicated, e.g. two-way valves with electronic monitoring system and complicated safety controls.